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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 14th May 2020, 11:27 pm   #21
Techman
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Default Re: Home made Wartime transmitter /receiver

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Originally Posted by HamishBoxer View Post
PX25,s oh well they will not be worth much!!Thank you I must dig out the old R/Bygones.
No, not worth much - ten a penny

Those valves look too big to be PX4s, so are likely to be PX25s, which I think the military possibly used as modulators in transmitters.
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Old 15th May 2020, 11:25 am   #22
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Default Re: Home made Wartime transmitter /receiver

I remember, in my youth, I acquired an amplifier that had been used on a fairground- playing Del Shannon "Runaway" on the dodgems, that sort of thing. PP 807s with 350v on them, guessing about twenty watts. To my ears it worked ok with the Fane speaker I had. Somehow I discovered that it was transmitting RF on Medium Wave and I could pick up the music on a transistor radio at a range of 100 yards or so. Must have been some instability in that amp, not needing any modification whatsoever. It wouldn't have made a good spy Tx, not portable as it weighed a fair bit!
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Old 15th May 2020, 2:04 pm   #23
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Default Re: Home made Wartime transmitter /receiver

I had a look in the second edition of "The Radio Amateur Handbook". This was originally published in July 1940, but my version is an August 1944 reprint.

I also looked at RSGB Bulls from 1939.

Common receiver valves used in home buit transmitters were the 6L6G and 6VG. Unsurprisingly published designs for transmitters dried up after the outbreak of WW2 and the Bulls got smaller due to paper shortages/rationing.

The adaptors used by the Germans could be used in receivers having AL4, AL5, EL2, EL12, 6L6 and 6V6 output valves. Annike could have modified a receiver using one of the valves without the use of an adaptor.

Let me know what further info you need. Presumably the construction of the kit is to be described in the novel, but it's difficult to know what would actually fit in with the plot.

As for the Royal Signals transmitter/receiver this would presumably have been relatively high powered, rather than the low power sets such as the 19 set used in tanks etc?
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Old 15th May 2020, 3:37 pm   #24
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Default Re: Home made Wartime transmitter /receiver

Thank you Graham, yes it must have been pretty high powered the Royal Signals set.

I will try and put something together and send it to the writer. My gosh there has certainly been a good few postings from all, which has been very helpful.
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Old 15th May 2020, 7:43 pm   #25
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Default Re: Home made Wartime transmitter /receiver

One thing that will need to be dealt with is the question of determining the Tx frequency.

A small simple transmitter would require crystal control, and crystals were understandably almost impossible to obtain. Anyone caught trying to source one, or worse still in possession, would be assumed to be an enemy spy. The death penalty might be applicable, it certainly was on the other side of La Manche...

A sufficiently stable VFO would most likely be beyond the skills of a casual builder and add too much to the cost, size, and complexity of the set.

The search for a suitable crystal could make for quite a sub-plot. Maybe something could turn up eventually and have to be re-ground as necessary?

The classic pre-WW2 British transmitter valve was the KT8, nowhere near as good as an 807 but a lot smaller in size. But like a crystal it would be shouting *TRANSMITTER!* and a dead giveaway. Better to stick with a standard audio output valve like a 6L6 as suggested above.
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Old 15th May 2020, 9:55 pm   #26
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Default Re: Home made Wartime transmitter /receiver

I'd forgotten about the transmit crystal, one would certainly have been needed.

How about taking one from the radio in a crashed aircraft? Or finding one laying on the ground after the wreckage had been taken away for scrap? Steal one from the villans thereby thwarting their operation?

They'd also have needed some pretty thick wire for the tank coil.

What about the morse key? I've manged quite well touching wires together or even wrapping wires round thumb and first finger. Not recommended for keying valve transmitters though!
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Old 16th May 2020, 9:16 am   #27
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Default Re: Home made Wartime transmitter /receiver

Why would it need a crystal? A well built VFO is quite stable enough at HF.
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Old 16th May 2020, 3:33 pm   #28
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Default Re: Home made Wartime transmitter /receiver

This discussion has reminded me of the book "Sonja's Report", see:-

https://en.wikipedia.org/wiki/Ursula_Kuczynski

This entry says that she trained to build a receiver which she used operationally. I would say that if someone is capable of building a receiver, probably a TRF, then they would have no trouble building a one-lunger TX like the Paraset or using something like the plug-in adaptors mentioned earlier. In this case the lady was working for the Soviets but the above would apply whatever country she was spying for.


73

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Old 16th May 2020, 11:53 pm   #29
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Default Re: Home made Wartime transmitter /receiver

Were crystals in short supply during the war? I've often wondered why eg the ubiquitous T1154 wasn't crystal controlled, to save on that complex L/C resetting mechanism. The TX could have been a lot smaller.
Setting up the 1154s before a raid was a dead giveaway to the German Y service.
Doesn't the quartz used in crystals come from Brazil?
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Old 17th May 2020, 7:53 am   #30
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Default Re: Home made Wartime transmitter /receiver

When the Australian Army "Sparrowforce" were stranded behind enemy lines in Timor, following the rapid Japanese advance, they managed to avoid capture, & spent their time harassing the enemy.

Their problem was, that nobody in Australia knew they were still active, & supplies were getting low.

To this end, they constructed a CW transmitter they called "Winnie the War winner".
(I have seen what is either the original, or a faithful reproduction at the Australian War Museum.)

I don't know what they did for a receiver, but for the Tx, they dug through rubbish tips for bits, & also salvaged some parts which had been buried to deny them to the enemy, but it was still slim pickings, so they had to stretch to stealing parts from the Japanese.

Finally, they made contact with Darwin, who were understandably suspicious, but after an operator recognised the Timor operator's "hand" were more
inclined to believe.

Still, it was only after they had a friend of one of the Timor group ask questions that only the real person could answer, that Darwin was convinced.

Sparrowforce stayed in Timor, & was re-supplied, including with new radio equipment, & "Winnie" was gratefully retired.
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Old 17th May 2020, 8:06 am   #31
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Default Re: Home made Wartime transmitter /receiver

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Originally Posted by CarbonMike View Post
Were crystals in short supply during the war? I've often wondered why eg the ubiquitous T1154 wasn't crystal controlled, to save on that complex L/C resetting mechanism. The TX could have been a lot smaller.
Setting up the 1154s before a raid was a dead giveaway to the German Y service.
Doesn't the quartz used in crystals come from Brazil?
Certainly, the German armed forces had problems with supplies of crystals and that led to their use of very high stability capacitors that were machined onto radio chassis. Yes, Brazil was the prime supplier to Allied countries.

The RAAF introduced an add-on crystal oscillator box for their T1154s after WW2 and I think an airline did the same. FWIW, I worked a station on VE Day last week who was using an 1154, let's just say it had a "distinctive" note!

Cheers

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Old 17th May 2020, 8:12 am   #32
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Default Re: Home made Wartime transmitter /receiver

Fascinating story! There's more here, thanks for the info:-

https://en.wikipedia.org/wiki/Winnie_the_War_Winner

Cheers

Roger
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Old 23rd May 2020, 5:32 am   #33
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Default Re: Home made Wartime transmitter /receiver

Here in the U.S., with all ham activity shut down, some of the guys built Carrier Current sets and transmitted over the power lines or wire fences. (Think large cattle ranches with miles of fence, and the next ham connecting to the fence to receive the signals at the next ranch.)
To this day, the power company still uses carrier current for some of the "smart power meter" monitoring.
They were so concerned about "Alien Agents" here that they removed all but the broadcast band coils from SW receivers owned by people of Japanese descent so they couldn't receive "espionage messages" on the radios. Sadly, most of the folks were loyal Americans in the U.S. "Internment/ concentration" camps. My dentist was in one of them as a child.
I did finally get one of the modified radios for my collection.
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